Method and apparatus for controlling the position of strip material in furnaces



June 8, 1965 A cos'rmqs 3 188,063

1 METHOD AND APPARATUS FOR CONTROLLING THE POSITION OF STRIP MATERIAL IN FURNACES Filed July 18, 1963 2 Sheets-Sheet l FIG. I

INVENTOR. ANDREW L OOSTAKIS TTOR NE Ys.

AA. L. COSTA 3,188,063 ITION June 8, 1965 5 7 METHOD AND APPAR TUS FOR CONTROLLING THE POS 0F STRIP MATERIAL IN FURNACES Filed July 18, 1965 2 Sheets-Sheet 2 FIG. 2

INVENTOR. ANDREW L. COSTAKIS ATTORNEYS.

United States Patent Ofiice 3,188,663 Patented June 8, 1965 METHUD AND APPARATEE FGR CGNTRULLENG THE Pfifiiiltlthi F ST MATEREAL IN FURNACES Andrew L. Costalris, Highland, 1nd,, assignor to Nationai teel Qorporation, a corporation of Deiaware Filed July 18, 1963, Ser. No. 295,945

12 Claims. (Cl. 263-3) The present invention relates to methods and apparatus for controlling the position of strip material in furnaces.

In the feeding of indeterminant lengths of strip material over rolls, various factors tend to cause the strip to move toward one end or the other of the rolls and thus to become misaligned relative to the rolls. A number of systems for correcting the positional error of the strip have been proposed and many are quite useful in ordinary operations. But in the environment of a furnace which is entirely enclosed in order to conserve heat or to maintain an inert atmosphere to prevent oxidation of the strip, the ordinary devices for controlling the position of the strip are unavailable for use because the rolls are entirely within the furnace.

In the past, it has been proposed to center strip in furnaces by centering the strip immediately before it enters the furnace, and then keeping it centered in the furnace by providing self-centering rolls or crowned rolls or other types of rolls in the furnace which by their physical configuration tend to center the strip. However, even with the practice of such preventative measures, it has been found that the strip still tends to become misaligned and to veer off the roll in the furnace, with the result that the furnace structure is damaged by the rapidly moving strip and the rapidly moving strip is damaged by the furnace structure.

It has now been discovered that variations in strip thickness transversely of the strip are responsiblefor at least a substantial portion of the misalignment that occurs within the furnace. It has also been discovered that when-the material enters the furnace and rises rapidly in temperature toward the temperature of the furnace, variations in strip thickness transversely of the width of the strip tend to cause the strip to expand unevenly at least at first, and this in turn tends to throw the strip laterally off its intended path of travel, thereby misaligning the strip relative to the rolls. The present invention also comprises the discovery of methods and apparatus for correcting the strip misalignment that occurs in this and other ways in the furnace.

Accordingly, it is an object of the present invention to provide methods and apparatus for centering strip on rolls while the strip is passing through a furnace of the type that encloses a plurality of rolls about which the strip passes along a circuitrous path.

Another object of the present invention is the provision of such methods and apparatus that will reduce or prevent damage to the strip during passage'through the furnace.

Still another object of the present invention is the provision of such methods and apparatus that will reduce or prevent damage to the furnace resulting from the passage therethrough of strip material.

Finally, it is an object of the present invention to provide such methods that will be relatively easy to practice and dependable in their result, and to provide such apparatus that will be relatively simple and inexpensive to manufacture, install, operate, maintain and repair, and rugged and durable in use.

Other objects and advantages of the present invention will become apparent from a consideration of the folr of the strip.

lowing description, taken in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic elevational view, with parts broken away, of one embodiment of a furnace according to the present;

FIGURE 2 is an enlarged fragmentary view of the region indicated by the line 22 in FIGURE 1;

FIGURE 3 is an enlarged fragmentary view of the region indicated by the line 33 in FIGURE 1.

Referring now to the drawings in greater detail, there is shown in FIGURE 1 a furnace comprising an enclosure 1 through which strip material 3 such as steel strip to be treated at elevated temperature passes in a circuitous path between an entrance 5 and an exit 7 of the furnace enclosure above a series of rolls 9 that bend the strip material into a plurality of loops or bights to assure that the strip material will have a sufficiently long residence time in the furnace to enable the heat treatment in question to be carried out. Each loop or bight is characterized by a pair of elongated generally straight length of strip in the form of passes 11, 13, 15, 17, 19, 21, 23, 25, 2'7 and 29, in that order from entrance 5 to exit 7. Of course, the particular number of passes is variable over a wide range and forms no part of the present invention. Suffice it to say that each pass is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement. The structure of the furnace thus far described may be generally conventional apart from the present invention and may include the usual heating means (not shown).

The present invention includes novel structure in the form of means inside enclosure 1 for detecting lateral misalignment of the strip relative to the rolls, and means outside the enclosure 1 responsive to to the first-named means for altering the lateral position of the strip prior to the entry of the strip into the enclosure. As is seen in FIGURES l and 2, a particular embodiment of the detector means is shown in the form of a photoelectric device 31 comprising a light source 33 that directs light toward a detector unit 35, comprising a pair of sensors 37 and 39. The light from the light source passes one edge 41 of strip 3. When strip 3 is properly aligned relative to the rolls 9 within the furnace, edge 41 will occupy the position shown in full line at 43 in FIGURE 2. In that position, light from light source 33 will shine on sensor 39, but sensor 37 will be masked by the edge In one position of misalignment, when the strip is too far to the left as seen in FIGURE 2, edge 41 occupies the position 45 shown in broken line in FIG- URE 2 and both of sensors 37 and 39 are photo-actuated. In another position of misalignment, in which the strip is too far to the right as seen in FIGURE 2 and the edge 41 of the strip occupies the position shown by the broken line at 47 in FIGURE 2, both of sensors 37 and 39 are masked from the light source by the strip.

Electrical impulses from detector unit 35 are conducted along line 49 to a regulator 51, which in turn regulates apower unit 53 which directs fluid under pressure through one or another of a pair of conduits 55 and 57 to a fluid motor 59 to opposite sides of a piston 61 that reciprocates Within a cylinder 63 and thus reciprocally actuates a piston rod 65 that is pivotally connected to one end of a shaft 6'7 on which is carried a roll 69 about which a bight of strip 3 is looped immediately prior to entry of the strip into the furnace. The other end of shaft 67 is pivotally mounted on a support 71 so that roll 69 is mounted for movement relative to the rolls 9 within the enclosure 1 between first and second positions characterized in that the axis of roll 69 in a first position is disposed at an acute angle to the axis of roll 69 in a second position. In other words, roll 69 is power driven by fluid motor 59 to swing through small acute angles.

The tilting of roll 69 causes strip 3 to move laterally of itself on roll 69. FIGURE 3 illustrates this movement. As is seen in broken lines in FIGURE 3, when the axis of roll 69 is perpendicular to the direction of movement of strip 3, strip 3 will be centered on roll 69 and edge 41 of strip 3 will occupy the position shown in broken line at 73 in FIGURE 3. But when roll 69 is canted in either direction, strip 3 will move laterally on it in such a way that the strip seems to climb the incline of the roll. Thus, as is seen in FIGURE 3 in full line, when roll 69 is swung counterclockwise as seen in that figure, strip 3 moves to the right as seen in FIGURE 3 until edge 41 of strip 3 occupies the position shown in full line at 75. Of course, swinging roll 69 counterclockwise would cause strip 3 to shift to the left of FIGURE 3; and if roll 69 were swung until it occupied a position inclined downwardly to the right as seen in FIGURE 3, then edge 41 of strip 3 would move past position 73 to the left as seen in FIGURE 3 until the strip was misaligned in the opposite sense from the misalignment shown in full lines in FIGURE 3.

In other words, the present invention is characterized by aligning the strip inside the furnace regardless of whether the strip outside the furnace is aligned or not. In many instances, therefore, the practice of the present invention results in a deliberate misalignment of the strip outside the furnace, which is in sharp contrast to the prior art practices in which the strip was aligned outside the furnace and an elfort was made to keep it aligned within the furnace.

Another important feature of the invention is concerned with the position of the alignment detector within the furnace. As was stated above, a portion of the present invention is discovery that at least a portion of the strip and furnace damage occurring when an aligned strip is fed into the furnace results from the fact that the heat striking a strip of uneven cross sectional configuration causes it to veer laterally relative to the rolls of the furnace. Another portion of the invention, however, is the discovery that this veering tends to correct itself within the furnace as the strip attains a uniformly high temperature, so that strip can enter the furnace aligned and leave the furnace aligned but be so badly misaligned within the furnace that damage results both to the strip and to the furnace. It has been determined that the damaging misalignment takes place at least principally less than half way along the length of the strip within the enclosure relative to the direction of movement of the strip within the enclosure, so that the misalignment detector should be disposed no farther along in the furnace than the first half of the total number of passes. In the embodiment of FIGURE 1, therefore, the detector should be no farther along than pass 19.

It has also been determined that damaging misalignment does not manifest itself until toward the end of the first pass, so that the detector should be disposed no farther toward the entrance of the furnace, with respect to the direction of travel of the strip, than adjacent the roll 9 at the end of the first pass 11. The position of the detector in FIGURE 1 is therefore about as close to the entrance end of the furnace along the strip as is desirable.

In the other direction, toward the exit of the strip from the furnace, there is more latitude for placement of the detector, but it is still preferred not to position the detector much beyond the third pass, and preferably not much beyond the second pass. Therefore, the most preferred position for the detector is adjacent the second pass, it being understood that the term adjacent must be construed so that there is substantially more latitude in the direction from the second pass toward the exit than there is from the second pass toward the entrance of the furnace.

To illustrate operation of the apparatus of the present invention and the practice of the corresponding method, let it be assumed that strip is passing over the roll 69 and about the rolls 9 within the furnace with the strip within the furnace centered as seen in full line in FIGURE 2 within the furnace and centered on the roll 69 with the roll 69 disposed horizontally as shown in phantom line in FIGURE 3. Assume that a stretch of strip is reached which has uneven cross-sectional configuration and that when heat strikes the strip the strip shifts laterally on the rolls 9 within the furnace until the edge 41 of the strip moves from the position 43 shown in full line in FIGURE 2 to the position 45 shown in broken line in FIGURE 2. During the time that the strip was centered on the rolls 9 within the furnace, sensor 37 was masked by the strip edge and sensor 39 was disposed so that light struck and actuated sensor 39, so that a signal was sent to regulator 51 and fluid power unit 53 was so regulated that fluid under pressure was not sent in either direction through conduits 55 and 57 to fluid motor 59. In other words, roll 69 remained horizontal and disposed in the broken line position of FIGURE 3.

But let it now be assumed that a section of strip 3 enters the furnace and has an uneven cross-sectional configuration such that when heat strikes the strip, although the strip is centered on roll 69, it nevertheless deflects soon after it enters the furnace and veers off to the left as seen in FIGURE 2 until edge 41 of the strip occupies the position shown in broken line at 45. Upon the attainment of this or a more exaggerated condition, sensor 37 is exposed and both of sensors 37 and 39 are activated by the light from light source 33 and a signal is sent to regulator 51 and thence to fluid power unit 53 such that fluid is sent through conduit 55 to the underside of piston 61 and fluid is exhausted from the upper side of piston 61 through conduit 57, to the end that roll 69 is raised counterclockwise as seen in FIGURE 3. Strip 3 tends to climb up roll 69, as was noted above, until the parts are in the position shown in full line in FIGURE 3 with the edge 41 of the strip occupying position 74. Inside the furnace, however, as seen in FIGURE 2, this movement of roll 69 and strip 3 outside the furnace serves to return the edge 41 of strip 3 from the position 45 back to the full line position 43, whereupon sensor 37 is covered and sensor 39 remains uncovered so that no further fluid flows through either of conduits 55 and 57.

Should the strip return to a uniform rectangular crosssectional configuration, then edge 41 of strip 3 would tend to move from the full line position 43, as shown in FIG URE 2, to the right of FIGURE 2 until it occupied broken line position line 47, whereupon both the sensors 37 and 39 would be covered and the signal would be sent to regulator 51 so as to send fluid through conduit 57 and exhaust it from conduit 55 thereby lowering piston 61 and piston rod 65 to the extent necessary to return roll 69 to a horizontal position, whereupon strip 3 will tend to move to the left along roll 59 until sensor 39 is uncovered but not sensor 37.

From a consideration of the foregoing disclosure, therefore, it will be obvious that all of the initially recited objects of the present invention have been achieved.

Although the present invention has been described and illustrated in connection with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

What is claimed is:

1. In a method of heating strip material passing continuously through an entirely enclosed furnace, the steps comprising detecting lateral misalignment of strip maerial solely within'the furnace, and altering the lateral position of the strip prior to entry of the strip into the furnace in a direction to correct the lateral misalignment of the strip solely within the furnace, regardless of whether the strip outside the furnace is aligned or not.

2. In a method of heating strip material passing continuously through a furnace, the steps comprising detecting lateral misalignment of the strip material within the furnace at a point on the strip less than half way along the length of the strip in the furnace relative to the direction of movement of the strip through the furnace, and altering the lateral position of the strip prior to entry of the strip into the furnace in a direction to correct the lateral misalignment of the strip within the furnace.

3. In a method of heating strip material passing continuously through a furnace with the strip material having a sinuous configuration within the furnace characterized by a plurality of alternately generally oppositely moving passes, the steps of detecting lateral misalignment of the strip material within the furnace at a point adjacent the second pass, and altering the lateral position of the strip prior to the entry of the strip into the furnace in a direction to correct the lateral misalignment of the strip within the furnace.

4. A furnace comprising an enclosure, a plurality of rolls within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement, means inside the enclosure for detecting lateral misalignment of the strip relative to the rolls, and means outside the enclosure responsive to the first-named means for altering the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

5. A furnace comprising an enclosure, a plurality of rolls within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement, means inside the enclosure for detecting lateral misalignment of the strip relative to the rolls at a point on the strip less than halfway along the length of the strip within the enclosure relative to the direction of movement of the strip through I the enclosure, and means outside the enclosure responsive to the first-named means for altering the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

6. A furnace comprising an enclosure, a plurality of 7 rolls within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement, means inside the enclosure for detecting lateral misalignment of the strip relative to the rolls at a point adjacent the second pass, and

means outside the enclosure responsive to the first-named,

means for altering the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

7. A furnace comprising an enclosure, a plurality of rolls within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement, means inside the enclosure for detecting lateral misalignment of the strip rela tive to the rolls, roll means disposed outside the enclosure and about which the strip passes on its'way to the enclosure, said outside roll means being mounted for movement relative to the rolls within the enclosure between first and second positions characterized in that the axis of said outside roll means in said first position is disposed at an acute vertical angle to said axis in said second position, and means responsive to the first-named means for moving said outside roll means between said first and second positions thereby to alter the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

8. A furnace comprising an enclosure, a plurality of rolls Within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement, means inside the enclosure for detecting lateral misalignment of the strip relative to the rolls at a point on the strip less than halfway along the length of the strip within the enclosure relative to the direction of movement of the strip through the enclosure, roll means disposed outside the enclosure and about which the strip passes on its way to the enclosure, said outside roll means being mounted for movement relative to the rolls within the enclosure between first and second positions characterized in that the axis of said outside roll means in said first position is disposed at an acute vertical angle to said axis in said second position, and means responsive to the first-named means for moving said outside roll means between said first and second positions thereby to alter the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

9. A furnace comprising an enclosure, a plurality of rolls within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement, means inside the enclosure for detecting lateral misalignment of the strip rela tive to the rolls at a point adjacent the second pass, roll means disposed outside the enclosure and about which the strip passes on its way to the enclosure, said outside roll means being mounted for movement relative to the rolls within the enclosure between first and second positions characterized in that the axis of said outside roll means in said first position is disposed at an acute vertical angle to said axis in said second position, and means responsive to the first-named means for moving said outside roll means between said first and second positions thereby to alter the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

it). A furnace comprising an enclosure, a plurality of rolls within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement, photoelectric means within the enclosure adjacent an edge of the strip and responsive to the amount of light that passes the edge of the strip for detecting lateral misalignment of the strip relative to the rolls, and means outside the enclosure responsive to the photoelectric means for altering the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

11. A furnace comprising an enclosure, a plurality of rolls within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two roll adjacent to each other with regard to the direction of strip movement, photoelectric means Within the enclosure adjacent an edge of the strip at a point on the strip less than halfway along the length of the strip within the enclosure relative to the direction of movement of the strip through the enclosure and responsive to the amount of light that passes the edge of the strip for detecting lateral misalignment of the strip relative to the rolls, and mean outside the enclosure responsive to the photoelectric means for altering the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

12. A furnace comprising an enclosure, a plurality of rolls within the enclosure for the support of continuously moving strip material as it moves through the enclosure in a circuitous path characterized by a plurality of passes each of which is a relatively straight section of strip between two rolls adjacent to each other with regard to the direction of strip movement, photoelectric means Within the enclosure adjacent an edge of the strip at a point adjacent the second pass and responsive to the amount of light that passes the edge of the strip for detecting lateral misalignment of the strip relative to the rolls, and means outside the enclosure responsive to the photoelectric means for altering the lateral position of the strip prior to the entry of the strip into the enclosure in a direction to correct the lateral misalignment of the strip within the furnace.

References Cited by the Examiner UNITED STATES PATENTS CHARLES SUKALO, Primary Examiner.

JOHN J. CAMBY, Examiner. 

1. IN A METHOD OF HEATING STRIP MATERIAL PASSING CONTINUOUSLY THROUGH AN ENTIRELY ENCLOSED FURNACE, THE STEPS COMPRISING DETECTING LATERAL MISALIGNMENT OF STRIP MATERIAL SOLELY WITHIN THE FURNACE, AND ALTERING THE LATERAL POSITION OF THE STRIP PRIOR TO ENGRY OF THE STRIP INTO THE FURNACE IN A DIRECTION TO CORRECT THE LATERAL MISALIGNMENT OF THE STRIP SOLELY WITHIN THE FURNACE, REGARDLESS OF WHETHER THE STRIP OUTSIDE THE FURNACE IS ALIGNED OR NOT. 